The present invention relates to improvements in electromotors, especially brushless motors. In known electromotors of the brushless type, the tensile forces conducted through the electrical lines into the motor are absorbed such that they are guided into the motor housing by way of a form fit. It is also known to secure the electric lines by means of the known principle of rope friction. Preferably, a separate component is used for the purpose of implementing the rope friction concept. Typically, the component is embodied in the form of a labyrinth and, after the flexible electrical lines have been inserted, this labyrinth is attached by means of a bracket. The tensile forces are conducted into the motor housing by way of this labyrinth with its affixed bracket, producing high stresses in the motor housing. This requires a very sturdy construction. In addition, a large portion of the construction space of the entire electromotor is taken up thereby, such that correspondingly less construction space is available for the electrical or magnetic part of the electromotor. Thus, there is little usable construction space in the motor relative to the total construction space. This results in lower performance of the electromotor in the context of the given construction space.
In an electromotor of the brushless type, the flexible electric lines are often sprayed with a closed-pore elastomeric material with a low degree of ductility, with this material being conventionally used as an insulation and sealing medium for protecting the electric and electronic components arranged in the electromotor from chemical and mechanical influences, such as vibrations.
The present invention is directed to addressing the prior art problems just discussed.
In a known electromotor of this type, expensive measures are necessary to achieve sufficient relief of line tension; therefore, a primary object of the present invention is to create an electromotor that is simple to mount with few components. This object is attained in accordance with the invention in that securing of the flexible electric lines in a fixed position is guaranteed in all spatial directions solely by a hardenable plastic material, whereby the connections do not need to absorb or transfer any mechanical forces, in particular tensile forces.
It is another object of the present invention to create an electromotor, with its given constructed size, good impermeability, and high mechanical loading capacity, that is not only simple to mount with few components, but ideally allows an optimal use of the electrically and/or magnetically usable construction space with a total construction space that is as large as possible.
These and other objects and advantages are in the present invention, which comprises an electromotor, in particular, a brushless pump motor that is made up of essentially a motor housing, a stator winding, and a circuit board. Flexible electrical lines are guided through the motor housing in a passage and electrically connected to the circuit board by way of connections. Hollow spaces defined in the motor housing are partially or completely filled with a hardenable plastic material. The flexible electrical lines run between their connections to the circuit board and the passage of the motor housing with a total change in direction amounting to at least 40xc2x0 and are arranged in at least one of the hollow spaces of the motor housing that is filled with hardenable plastic material such as polyurethane foam. In this way, the flexible electrical lines are essentially completely surrounded by the hardenable plastic material at least in the regions of the changes in direction in the progression of the electric lines.
By using the known principle of rope friction, the changes in direction in the progression of the flexible electric lines allow high resistance to slippage of the flexible electric lines. In this connection, the form and/or direction in which these changes in direction occur are immaterial.
In the present invention, fixing of the flexible electric lines is guaranteed in all spatial directions by the hardenable plastic material alone, whereby the connections need not absorb or transfer any mechanical forces, particularly tensile forces. The hardenable plastic material not only serves as a seal, but also serves as a tension relief in all spatial directions. The tension relieving effect is determined solely by the properties of the hardenable plastic material and the geometric arrangement of the flexible electric lines, with additional components being omitted as tension relievers. The greatest possible use of the electrically and/or magnetically useable construction space relative to the total construction space is achieved by means of a motor housing with walls as thin as possible. This can be realized if the tensile forces acting on the flexible electrical lines are transferred over a large area by way of the hardenable plastic mass into the motor housing.
An excellent impermeability is achieved with the electromotor in accordance with the invention in that the hardenable plastic reaches a foam-like, preferably closed-pore, state as a result of an expansion process. In this manner, the hardened plastic nuzzles itself against the motor, limited by the motor wall, and surrounds static components located in the interior of the motor.
In the present exemplary embodiment, the motor housing comprises a housing cover and a one-piece or assembled housing pot. The housing cover serves to facilitate the mounting of the flexible electric lines in a defined bent progression in that one-piece guides are provided on the housing cover. The bent progression is a precondition for secure tension relief in all-spatial directions. In a preferred embodiment, the guides are in the form of protruding risers or pins. Because the guides do not have to perform a tension relief function, they do not completely surround the flexible electric lines. Thus, they can additionally be structured in a material- and space-saving manner.
In their mounted state, the guides reach approximately up to the circuit board and they are formed in such a way that, in their mounted state, they enter into a frictional and/or form-fitting connection with the hardenable plastic material in the axial direction. By means of this measure, a secure fixture of the housing cover on the housing pot is achieved. This arrangement thus eliminates the need for an expensive additional connection between the housing cover and the housing pot.
It is self-evident to provide motor housings with at least one opening to facilitate the introduction of the hardenable plastic material inside the motor housing. For the purpose of pressure relief during filling, it is useful to provide two openings in the housing cover.
A particularly helpful measure to facilitate introduction of the hardenable plastic material is the arrangement of a bushing between the flexible electrical lines and their passage in the motor housing. The bushing tightly surrounds the flexible electric lines and the motor housing in such a way that the hardenable plastic mass cannot escape out of the housing in its fluid state. In like manner, the housing cover seals off the housing pot with a mounted bush.
In order to achieve a particularly secure relief of tension, the flexible electric lines in the motor housing preferably run in a loop, i.e., with the greatest possible total change in direction in the smallest space.
A further improved tension relief results if the hardenable plastic material approximately completely fills the space between the housing cover and the circuit board because the hardenable plastic material can then connect on a large surface with the formations of the housing and the circuit board with a form-fitting and/or frictional and/or material connection.
So that the connection between the housing pot and the hardenable plastic material is also sufficient, it is recommended that the housing pot be formed in such a way that a form-fitting and/or frictional and/or material connection is present between the housing pot and the hardenable plastic material.
In order to be able to economically mount the electromotor in accordance with the invention, two mounting sequences are recommended.
In accordance with the first recommended sequence, a first construction unit comprising a wound stator core and the circuit board provided with the electric lines is first inserted into the motor pot. Then the flexible electric lines are inserted into the guides of the housing cover. With the positioning of the motor cover relative to the motor housing being established by means of the bush, the motor cover is inserted into the motor housing. Then, the motor housing is filled with the hardenable plastic material through at least one opening in the motor housing, and finally the plastic material is allowed to harden.
In accordance with the second recommended sequence, the wound stator core is mounted in an assembled condition in the second construction unit with the circuit board and the connection lines, and then the flexible electric lines are inserted into the guides of the housing cover. The arrangement of the third construction unit of the circuit board and the flexible electric lines, and the housing cover to the motor housing is produced and oriented to fit in the motor pot 11. The motor housing is filled with the hardenable plastic material through at least one opening in the motor housing, and finally the hardenable plastic material is allowed to harden.
Exemplary embodiments of the invention will be explained in greater detail in the following with reference to the drawings.